Former president George W. Bush underwent knee surgery over the weekend for the second time since May.

Bush spokesman Freddy Ford said Bush’s left knee was partially replaced Saturday at Rush University Medical Center’s Midwest Orthopaedics — the same place where he had partial knee replacement on his right knee over Memorial Day weekend.

“President and Mrs. Bush are on their way back to Dallas this morning,” Ford said Monday in a statement. “He’s looking forward to getting back on his mountain bike in a few weeks.”

Bush, who turned 68 on July 6, is an avid mountain bike rider and annually hosts a rigorous riding event to honor servicemembers wounded in Iraq and Afghanistan.

Bush’s outpatient surgeries were performed by Dr. Richard Berger of Midwest Orthopaedics.

Knee replacement surgery has become common, especially among people over 50. An estimated 645,000 total knee replacement procedures were performed in 2011, according to statistics from the American Academy of Orthopaedic Surgeons.